Vehicular battery control device

ABSTRACT

A vehicular battery control device controls an electric storage amount of a battery as which a lithium-ion battery is employed. The vehicular battery control device includes a control unit that reduces the electric storage amount of the battery until the electric storage amount of the battery assumes a second state, before the lapse of a first time, when the electric storage amount of the battery assumes a first state and it is predicted that a charge current will flow in the first time. The first state is a state where lithium metal is precipitated by charging the battery with a predetermined amount of electric power, and the second state is a state where no lithium metal is precipitated even when the charge current flows through the battery.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2019-000780 filed onJan. 7, 2019 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a vehicular battery control device thatcontrols an electric storage amount of an in-vehicle battery as which alithium-ion battery is employed.

2. Description of Related Art

In Japanese Patent Application Publication No. 2015-156357 (JP2015-156357 A), there is disclosed an electric power supply systememploying a lithium-ion battery. In the electric power supply system ofthis Japanese Patent Application Publication No. 2015-156357 (JP2015-156357 A), the temperature of the lithium-ion battery is raised toa predetermined temperature range through the performance ofcharge/discharge by a control unit, such that the lithium-ion batterycan achieve a favorable performance.

SUMMARY

The art described in Japanese Patent Application Publication No.2015-156357 (JP 2015-156357 A) is the control of raising the temperatureof the lithium-ion battery. However, there occurs a phenomenon ofprecipitation of lithium metal in the lithium-ion battery when thelithium-ion battery is further charged at a low temperature and with alarge electric storage amount. This precipitation of lithium metal maycause smoking and ignition, and deteriorates the safety of the battery.Therefore, there is room for consideration of a method of performingcontrol such that the lithium-ion battery whose temperature is low doesnot cause precipitation of lithium metal in the case where thelithium-ion battery is provided in an electric power supply system inwhich a charge current that makes it difficult to control thelithium-ion battery is produced, for example, a vehicular electric powersupply system.

The disclosure has been made in view of the aforementioned problem. Itis an object of the disclosure to provide a vehicular battery controldevice that can suppress the occurrence of precipitation of lithiummetal in a lithium-ion battery whose temperature is low.

In order to solve the above-mentioned problem, according to one aspectof the disclosure, there is provided a vehicular battery control devicethat controls an electric storage amount of an auxiliary battery or anautomatic driving backup battery as which a lithium-ion battery isemployed. The vehicular battery control device is equipped with adetermination unit that determines, based on a temperature of thebattery, whether or not the electric storage amount of the batteryassumes a first state where lithium metal is precipitated by chargingthe battery with a predetermined amount of electric power, a predictionunit that predicts, based on a running state of a vehicle, whether ornot a charge current corresponding to charge with the predeterminedamount of electric power will flow from a vehicle instrument connectedto the battery to the battery in a predetermined first time, and acontrol unit that reduces the electric storage amount of the batteryuntil the electric storage amount of the battery assumes a second statewhere no lithium metal is precipitated even when the charge currentflows through the battery, before lapse of the first time, when thedetermination unit determines that the electric storage amount of thebattery assumes the first state and the prediction unit predicts thatthe charge current will flow in the first time.

According to the vehicular battery control device of the aforementioneddisclosure, when it is predicted that the charge current leading toprecipitation of lithium metal in the in-vehicle battery will beproduced, the electric storage amount of the in-vehicle battery isreduced to an electric storage amount where no lithium metal isprecipitated. Thus, the occurrence of precipitation of lithium metal inthe lithium-ion battery whose temperature is low can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of anexemplary embodiment will be described below with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a view showing an exemplary schematic configuration of anelectric power supply system that includes a vehicular electric powersupply control device according to the present embodiment;

FIG. 2 is a view showing an exemplary relationship among a positiveelectrode potential, a negative electrode potential, and an electricstorage amount of a lithium-ion battery;

FIG. 3 is a view showing an exemplary temperature-SOC map thatrepresents the possibility of precipitation of lithium metal;

FIG. 4 is a processing flowchart of electric storage amount control A ofa battery that is performed by the vehicular electric power supplycontrol device;

FIG. 5 is a processing flowchart of electric storage amount control B ofthe battery that is performed by the vehicular electric power supplycontrol device;

FIG. 6 is a view illustrating a discharge path of a first battery; and

FIG. 7 is a view illustrating a discharge path of a second battery.

DETAILED DESCRIPTION OF EMBODIMENT

In a vehicular electric power supply control device according to thedisclosure, in the case where an in-vehicle battery assumes a state oflow temperature and large electric storage amount where lithium metalmay be precipitated when the in-vehicle battery is charged from itscurrent state, the electric storage amount of the in-vehicle battery isreduced to an electric storage amount where no lithium metal isprecipitated even when a charge current leading to precipitation oflithium metal flows through the in-vehicle battery, if it is predictedthat the charge current will be produced in the in-vehicle battery whilerunning in the future. Thus, the occurrence of precipitation of lithiummetal can be suppressed in the lithium-ion battery whose temperature islow.

Embodiment

The embodiment of the disclosure will be described hereinafter in detailwith reference to the drawings.

Configuration

FIG. 1 is a view showing an exemplary schematic configuration of anelectric power supply system 1 that includes a vehicular electric powersupply control device 40 according to the embodiment of the disclosure.The electric power supply system 1 exemplified in FIG. 1 is mounted in avehicle, and is equipped with a first electric power supply systemincluding an electric power supply unit 30, a DCDC converter (DDC) 11, afirst battery 12, a first automatic driving system 13, and an in-vehicleinstrument 14, a second electric power supply system including a secondbattery 22 and a second automatic driving system 23, and the vehicularelectric power supply control device 40.

In this electric power supply system 1, a redundant electric powersupply configuration that is composed of the first electric power supplysystem and the second electric power supply system is adopted. The firstelectric power supply system and the second electric power supply systemare connected to each other via a first relay device 51 for supplyingdark current. Besides, the first electric power supply system and thesecond electric power supply system are connected to each other via athird relay device 53 and a changeover DCDC converter (changeover DDC)60. The second battery 22 is connected to the changeover DCDC converter60 via a second relay device 52 for battery protection, and is furtherconnected to the second automatic driving system 23 via a fourth relaydevice 54. The connection/disconnection of this first relay device 51,this second relay device 52, this third relay device 53, this fourthrelay device 54, and this changeover DCDC converter 60 is controlled bythe vehicular electric power supply control device 40.

The electric power supply unit 30 can supply electric power to the DCDCconverter 11. A high-voltage battery configured in achargeable/dischargeable manner, for example, a lithium-ion battery orthe like is employed as this electric power supply unit 30.

The DCDC converter 11 can convert electric power that is supplied fromthe electric power supply unit 30, and output the converted electricpower to the first battery 12, the first automatic driving system 13,and the in-vehicle instrument 14. In concrete terms, the DCDC converter11 steps down high-voltage electric power that is supplied from theelectric power supply unit 30 to low-voltage electric power, and outputsthis low-voltage electric power to the first battery 12, the firstautomatic driving system 13, and the in-vehicle instrument 14.Incidentally, a plurality of DCDC converters 11 may be provided inparallel, in accordance with a purpose such as the enhancement ofconverter performance or the like.

The first battery 12 is an electric power storage element configured ina chargeable/dischargeable manner, for example, a lead storage battery,a lithium-ion battery or the like, and is a so-called auxiliary battery.In the present embodiment, a lithium-ion battery is employed as thefirst battery 12. This first battery 12 can accumulate (be charged with)the electric power that is output from the DCDC converter 11, and output(discharge) the electric power accumulated therein to the firstautomatic driving system 13 and the in-vehicle instrument 14.

The first automatic driving system 13 is a system including in-vehicleinstruments that are needed to automatically drive the vehicle. Forexample, an automatic driving electronic control unit (ECU), anelectrically operated brake device (EBS), an electrically operated powersteering device (EPS), and the like are included in the in-vehicleinstruments that are required for automatic driving.

The in-vehicle instrument 14 includes one or more in-vehicle instruments(auxiliaries) that are irrelevant to automatic driving of the vehicle.This in-vehicle instrument 14 includes, for example, devices such as aheadlamp, a wiper and the like.

The second battery 22 is an electric power storage element that isconfigured in a chargeable/dischargeable manner, for example, alithium-ion battery, a nickel hydride battery or the like, and is aso-called automatic driving backup battery. In the present embodiment, alithium-ion battery is employed as the second battery 22. This secondbattery 22 can accumulate (be charged with) the electric power that isoutput from the DCDC converter 11, and output (discharge) the electricpower accumulated therein to the first automatic driving system 13, viathe third relay device 53, the changeover DCDC converter 60, and thesecond relay device 52. Besides, the second battery 22 can output(discharge) the electric power accumulated therein to the secondautomatic driving system 23, via the second relay device 52 and thefourth relay device 54. This second battery 22 plays a role of a backupelectric power supply for maintaining the function regarding themovement of the vehicle in the case where the first battery 12 failsduring the driving of the vehicle.

The second automatic driving system 23 is obtained by redundantlyproviding the same system as the first automatic driving system 13. Asis the case with the first automatic driving system 13, the secondautomatic driving system 23 is a system including in-vehicle instrumentsthat are needed to automatically drive the vehicle.

The first relay device 51 is provided between the first electric powersupply system and the second electric power supply system, and isconfigured to be able to connect/disconnect the first electric powersupply system and the second electric power supply system to/from eachother, through the control of the vehicular electric power supplycontrol device 40. This first relay device 51 is connected when avehicle electric power supply is turned off at the time of parking orthe like, and forms a path for supplying dark current from the firstbattery 12 to the second automatic driving system 23. Otherwise, thefirst relay device 51 is disconnected, and electrically separates thefirst electric power supply system and the second electric power supplysystem from each other.

The changeover DCDC converter 60 and the third relay device 53 areprovided in series between the first electric power supply system andthe second electric power supply system, and is configured to be able toconnect/disconnect the first electric power supply system and the secondelectric power supply system to/from each other through the control ofthe vehicular electric power supply control device 40. The electricpower that is exchanged between the first electric power supply systemand the second electric power supply system when these systems areconnected to each other is controlled by the changeover DCDC converter60.

The second relay device 52 is provided between the second electric powersupply system side of the changeover DCDC converter 60 and the secondbattery 22, and is configured to be able to connect/disconnect thesecond electric power supply system and the second battery to/from eachother through the control of the vehicular electric power supply controldevice 40. This second relay device 52 is disconnected when the vehicleelectric power supply is turned off at the time of parking or the like,and prevents the consumption of current from the second battery 22 tothe second automatic driving system 23. Otherwise, the second relaydevice 52 is connected, and supplies electric power to the secondautomatic driving system 23.

The fourth relay device 54 is provided between the second electric powersupply system side of the changeover DCDC converter 60 and the secondautomatic driving system 23, and is configured to be able toconnect/disconnect the second electric power supply system and thesecond battery 22 to/from each other (via the second relay device 52)through the control of the vehicular electric power supply controldevice 40.

The vehicular electric power supply control device 40 can control thestate of the electric power supply system 1 by managing the states,operations and the like of the DCDC converter 11, the first battery 12,the second battery 22, the first relay device 51, the second relaydevice 52, the third relay device 53, the fourth relay device 54, andthe changeover DCDC converter 60. In the vehicular electric power supplycontrol device 40 of the present embodiment, the control for suppressingthe occurrence of precipitation of lithium in each of lithium-ionbatteries employed as the first battery 12 and the second battery 22 isperformed.

This vehicular electric power supply control device 40 can be configuredas an ECU that typically includes a processor, a memory, an input/outputinterface, and the like. The vehicular electric power supply controldevice 40 can include one, some or all of ECU's that are mounted in thevehicle, such as a monitoring ECU that can monitor voltages, currents,and temperatures of the first battery 12 and the second battery 22, anelectric power supply ECU that can control connection/disconnectionstates of the first relay device 51, the second relay device 52, thethird relay device 53, and the fourth relay device 54 and that cancontrol output voltages of the DCDC converter 11 and the changeover DCDCconverter 60, and the like. The vehicular electric power supply controldevice 40 of the present embodiment realizes the respective functions ofa determination unit 41, a prediction unit 42, and a control unit 43through the readout and execution of a program stored in the memory bythe processor.

The determination unit 41 determines, based on the temperature of eachof the first battery 12 and the second battery 22 as which thelithium-ion battery is employed, whether or not the electric storageamount of each of the batteries assumes the first state where lithiummetal is precipitated, when each of the batteries is charged with thepredetermined amount of electric power. Charge with the predeterminedamount of electric power can be set based on a maximum currentproducible in the vehicle, which is determined in accordance with thespecification, equipment and the like of the vehicle. The electricstorage amount where lithium metal is precipitated from the lithium-ionbattery is indicated as an electric storage amount (SOC) at the timewhen the negative electrode potential upon charging the lithium-ionbattery is lower than OV as a reference potential where lithium metal isdissolved and precipitated.

FIG. 2 shows an exemplary relationship between the positive electrodepotential and the negative electrode potential of the lithium-ionbattery and the electric storage amount (SOC) at a certain temperatureT. In the example of FIG. 2, the positive electrode potential and thenegative electrode potential at the time when the lithium-ion battery isnot charged are indicated by solid lines, and the positive electrodepotential and the negative electrode potential at the time when thelithium-ion battery is charged with the predetermined amount of electricpower are indicated by broken lines. This example of FIG. 2 reveals thatalthough there is no possibility of precipitation of lithium metalregardless of the electric storage amount of the lithium-ion batteryunless the lithium-ion battery is charged, lithium metal is precipitatedwhen the electric storage amount is equal to or larger than SOC-A in thecase where the lithium-ion battery is charged. This is ascribable to thefact that the difference in potential is enlarged through a rise in thepositive electrode potential and a fall in the negative electrodepotential as a result of a fall in internal resistance due to a chargecurrent and a polarization reaction. Under a condition of thetemperature T exemplified in FIG. 2, the electric storage amount SOC-Ais the electric storage amount of each of the first battery 12 and thesecond battery 22 that may become equal to or larger than the electricstorage amount where lithium metal is precipitated from the lithium-ionbattery.

The determination unit 41 holds in advance a temperature-SOC map (FIG.3) representing the possibility of precipitation of lithium metal, fromwhich the electric storage amount SOC-A at each temperature within apredetermined temperature range is obtained, and determines, based onthis temperature-SOC map, whether or not the electric storage amount ofeach of the first battery 12 and the second battery 22 assumes the firststate where lithium metal is precipitated by charging the battery withthe predetermined amount of electric power. The determination unit 41may hold a plurality of such temperature-SOC maps in accordance with acharge rate. For example, the determination unit 41 can hold twotemperature-SOC maps at the time of automatic driving and parking aswill be described later.

The prediction unit 42 predicts, based on a running state of thevehicle, whether or not a charge current corresponding to charge withthe predetermined amount of electric power will flow from the vehicleinstruments connected to the first battery 12 and the second battery 22,namely, the first automatic driving system 13, the in-vehicle instrument14, and the second automatic driving system 23 to the battery in apredetermined first time. In more concrete terms, it is predicted, basedon the running state of the vehicle, whether or not the charge currentthat cannot be controlled by the DCDC converter 11 and the changeoverDCDC converter 60 will flow through the first battery 12 and/or thesecond battery 22. The predetermined first time is set equal to orlonger than a time that is required from prediction by the predictionunit 42 to the completion of control by the control unit 43. Thefollowing scenes can be exemplified as scenes in which the chargecurrent that cannot be controlled by this DCDC converter flows throughthe battery.

The scenes are; (1) the scene in which current flows from the DCDCconverter to the battery until voltage control of the DCDC converterfollows a change in the supply of current in the case where the supplyof current to an electrically operated power steering device (EPS)becomes unnecessary after supplying a large current to the EPS, (2) thescene in which current flows from the DCDC converter to the batteryuntil voltage control of the DCDC converter follows a change in thesupply of current in the case where the supply of current to anelectrically operated brake device (EBS) becomes necessary aftersupplying a large current to the EBS, (3) the scene in whichregenerative current flows from a motor for EPS to the battery until asteering returns to a neutral position from a position where thesteering is steered at a maximum angle.

When the determination unit 41 determines that the electric storageamount of each of the first battery 12 and the second battery 22 assumesthe first state, the control unit 43 calculates a safe electric storageamount where no lithium metal is precipitated even when the battery ischarged with the predetermined amount of electric power. The safeelectric power storage amount is an electric storage amount in a secondstate in the temperature-SOC map exemplified in FIG. 3, and can becalculated based on the temperature of each of the first battery 12 andthe second battery 22. Then, the control unit 43 reduces the electricstorage amount of each of the first battery 12 and the second battery 22until the electric storage amount assumes the second state equal to orsmaller than the calculated safe electric storage amount, before thelapse of the first time predicted by the prediction unit 42.

The control according to the respective functions of the determinationunit 41, the prediction unit 42, and the control unit 43 that arerealized by the vehicular electric power supply control device 40 willbe described hereinafter in more detail.

Control

Electric storage amount control that is performed by the vehicularelectric power supply control device 40 according to the embodiment ofthe disclosure will be described with further reference to FIGS. 4 to 7.FIG. 4 is a flowchart showing a processing procedure of electric storageamount control (electric storage amount control A) of each of the firstbattery 12 and the second battery 22 that is performed by the vehicularelectric power supply control device 40 in automatic driving of thevehicle. FIG. 5 is a flowchart showing a processing procedure ofelectric storage amount control (electric storage amount control B) ofeach of the first battery 12 and the second battery 22 that is performedby the vehicular electric power supply control device 40 during parkingof the vehicle. FIG. 6 is a view illustrating a discharge path of thefirst battery 12. FIG. 7 is a view illustrating a discharge path of thesecond battery 22. Incidentally, the description of the followingflowcharts will be given by referring to each of the first battery 12and the second battery 22 simply as “the battery” in the case where eachof the first battery 12 and the second battery 22 is relevant.

(1) Electric Storage Amount Control A

The process shown in FIG. 4 is started by starting automatic drivingwith the electric power supply of the vehicle on (IG-ON).

In step S401, the determination unit 41 estimates the possibility ofprecipitation of lithium metal from the battery in the case where thebattery is charged with the predetermined amount of electric power. Thisestimation is carried out, based on the temperature of the battery andthe above-mentioned temperature-SOC map (FIG. 3), depending on whetheror not the electric storage amount of the battery assumes the firststate where lithium metal is precipitated in the case where the batteryis charged with a charge amount X of electric power that is determinedbased on the state of automatic driving.

In step S402, the determination unit 41 determines, as a result of theestimation in the aforementioned step S401, whether or not there is apossibility of precipitation of lithium metal from the battery. If thereis a possibility of precipitation of lithium metal from the battery (Yesin S402), the process proceeds to step S403. If there is no possibilityof precipitation of lithium metal from the battery (No in S402), theprocess proceeds to step S401.

In step S403, the prediction unit 42 predicts, based on the runningstate of the vehicle, whether or not the charge current corresponding tocharge with the predetermined amount of electric power will flow throughthe battery in the first time. In electric storage amount control A inthis automatic driving, the prediction unit 42 predicts, based on mapinformation or the like, whether or not the vehicle will run with alarge current corresponding to the charge amount X consumed in a firsttime t1, in a scheduled running path of the vehicle through automaticdriving. For example, running on a curve with the electrically operatedpower steering device in operation, or running on a downhill with theelectrically operated brake device in operation can be mentioned asrunning with the large current consumed that can be predicted based onmap information or the like. If the vehicle will run with the largecurrent consumed in the first time t1 (Yes in S403), the processproceeds to step S404. If the vehicle will not run with the largecurrent consumed in the first time t1 (No in S403), the process proceedsto step S406.

In step S404, the prediction unit 42 calculates the safe electricstorage amount where no lithium metal is precipitated from the batteryeven when the battery is charged with the large current corresponding tothe charge amount X. The safe electric storage amount is calculatedbased on the temperature of the battery and the above-mentionedtemperature-SOC map (FIG. 3). In the example of FIG. 3, when thetemperature of the battery remains the same, the safe electric storageamount for an electric storage amount A is determined as an electricstorage amount B. When the safe electric storage amount is calculated,the process proceeds to step S405.

In step S405, the control unit 43 reduces the current electric storageamount of the battery to an amount equal to or smaller than the safeelectric storage amount calculated in step S404. The reduction of thiselectric storage amount is carried out before the lapse of the firsttime t1 predicted by the prediction unit 42. When the battery to becontrolled is the first battery 12, the electric storage amount can bereduced by controlling the voltage of the DCDC converter 11 and forciblydischarging electric power from the first battery 12 to the firstautomatic driving system 13 and the in-vehicle instrument 14 as shownin, for example, FIG. 6. Besides, when the battery to be controlled isthe second battery 22, the electric storage amount can be reduced bycontrolling the connection states of the second relay device 52, thethird relay device 53, and the fourth relay device 54 and the voltage ofthe changeover DCDC converter 60, forcibly discharging electric powerfrom the second battery 22 to the second automatic driving system 23,and further discharging electric power from the second battery 22 to thefirst automatic driving system 13 and the in-vehicle instrument 14 aswell if necessary, as shown in, for example, FIG. 7. When the electricstorage amount of the battery becomes equal to or smaller than the safeelectric storage amount, the process proceeds to step S407.

In step S406, the control unit 43 maintains the current electric storageamount of the battery. Incidentally, if the electric storage amount ofthe battery has already been reduced to an amount equal to or smallerthan the safe electric storage amount in an immediately precedingprocess, the battery may be charged to the original electric storageamount without maintaining the electric storage amount of the battery.After that, the process proceeds to step S407.

In step S407, the vehicular electric power supply control device 40determines whether or not automatic driving of the vehicle has beenended. If automatic driving has not been ended (No in S407), the processproceeds to step S401. If automatic driving has been ended (Yes inS407), the present process is ended.

(2) Electric Storage Amount Control B

The process shown in FIG. 5 is started with the electric power supply ofthe vehicle on (IG-ON).

In step S501, the determination unit 41 estimates the possibility ofprecipitation of lithium metal from the battery when the battery ischarged with the predetermined amount of electric power. This estimationis carried out, based on the temperature of the battery and theabove-mentioned temperature-SOC map (FIG. 3), depending on whether ornot the electric storage amount of the battery assumes the first statewhere lithium metal is precipitated when the battery is charged with acharge amount Y that is determined based on the state of parking.

In step S502, the determination unit 41 determines, as a result of theestimation in the aforementioned step S501, whether or not there is apossibility of precipitation of lithium metal from the battery. If thereis a possibility of precipitation of lithium metal from the battery (Yesin S502), the process proceeds to step S503. If there is no possibilityof precipitation of lithium metal from the battery (No in S502), theprocess proceeds to step S501.

In step S503, the prediction unit 42 predicts, based on the runningstate of the vehicle, whether or not a charge current corresponding tocharge with a predetermined amount of electric power will flow throughthe battery in the predetermined first time t1. In electric storageamount control B during this parking, the prediction unit 42 estimatesthat the vehicle is about to be parked, depending on whether or not ashift position has been a reverse (backward) “R” position for a secondtime t2 or less, and predicts that a charge current Ic regenerated fromthe motor for EPS will flow through the battery in the first time t1. Ifthe shift position has been the R position for the second time t2 orless (Yes in S503), the process proceeds to step S504. If the shiftposition has not been the R position for the second time t2 or less (Noin S503), the process proceeds to step S506.

In step S504, the prediction unit 42 calculates a safe electric storageamount where no lithium metal is precipitated from the battery even whenthe battery is charged with a large current corresponding to the chargeamount Y. The safe electric storage amount is calculated based on thetemperature of the battery and the above-mentioned temperature-SOC map(FIG. 3). When the safe electric storage amount is calculated, theprocess proceeds to step S505.

In step S505, the control unit 43 reduces the current electric storageamount of the battery to an amount equal to or smaller than the safeelectric storage amount calculated in step S404. This reduction of theelectric storage amount is carried out before the lapse of the firsttime t1 predicted by the prediction unit 42. A forcible discharge pathfor reducing the electric storage amount of the battery to be controlledhas been described using FIGS. 6 and 7. When the electric storage amountof the battery becomes equal to or smaller than the safe electricstorage amount, the process proceeds to step S507.

In step S506, the control unit 43 maintains the current electric storageamount of the battery. Incidentally, if the electric storage amount ofthe battery has already been reduced to an amount equal to or smallerthan the safe electric storage amount in an immediately precedingprocess, the battery may be charged to the original electric storageamount without maintaining the electric storage amount of the battery.After that, the process proceeds to step S507.

In step S507, the vehicular electric power supply control device 40determines whether or not the vehicle has been parked. It can bedetermined that the vehicle has been parked, for example, when the shiftposition becomes a parking “P” position. If the vehicle has not beenparked yet (No in S507), the process proceeds to step S501. If thevehicle has been parked (Yes in S507), the present process is ended.

Operation and Effect

In the vehicular electric power supply control device 40 according tothe above-mentioned embodiment of the disclosure, in the case where theelectric storage amount of the battery (the first battery 12 or thesecond battery 22) as which the lithium-ion battery is employed is equalto the electric storage amount (the first state) where lithium metal maybe precipitated when the battery is charged from its current state, theelectric storage amount of the battery is reduced to the electricstorage amount (the second state) where no lithium metal isprecipitated, if it is predicted that the charge current leading toprecipitation of lithium metal will be produced while running in thefuture. Thus, the occurrence of precipitation of lithium metal can besuppressed in the lithium-ion battery whose temperature is low.

At this time, the electric power of the battery is prevented from beingwastefully consumed, by reducing the electric storage amount of thebattery by supplying electric power to the vehicle instruments (thefirst automatic driving system 13, the in-vehicle instrument 14, and thesecond automatic driving system 23) connected to the battery.

Incidentally, in the aforementioned embodiment, the case where both thefirst battery 12 and the second battery 22 are batteries as whichlithium-ion batteries are employed has been described. However, only oneof the first battery 12 and the second battery 22 may be a battery aswhich a lithium-ion battery is employed.

Although the embodiment of the disclosure has been described above, thedisclosure can be grasped as a vehicular electric power supply device,an electric power supply system including the vehicular electric powersupply control device, a method of estimating a full-charge capacitythat is carried out by the vehicular electric power supply controldevice, a program for estimating the full-charge capacity, acomputer-readable, non-transient recording medium in which the programis stored, or a vehicle mounted with the vehicular electric power supplycontrol device.

The vehicular electric power supply control device of the disclosure canbe utilized for a vehicle or the like that is mounted with a battery aswhich a lithium-ion battery is employed.

What is claimed is:
 1. A vehicular battery control device that controlsan electric storage amount of an auxiliary battery or an automaticdriving backup battery as which a lithium-ion battery is employed,comprising: a determination unit that determines, based on a temperatureof the battery, whether or not the electric storage amount of thebattery assumes a first state where lithium metal is precipitated bycharging the battery with a predetermined amount of electric power; aprediction unit that predicts, based on a running state of a vehicle,whether or not a charge current corresponding to charge with thepredetermined amount of electric power will flow from a vehicleinstrument connected to the battery to the battery in a predeterminedfirst time; and a control unit that reduces the electric storage amountof the battery until the electric storage amount of the battery assumesa second state where no lithium metal is precipitated even when thecharge current flows through the battery, before lapse of the firsttime, when the determination unit determines that the electric storageamount of the battery assumes the first state and the prediction unitpredicts that the charge current will flow in the first time.
 2. Thevehicular battery control device according to claim 1, wherein thecontrol unit reduces the electric storage amount of the battery bysupplying electric power to the vehicle instrument connected to thebattery.
 3. The vehicular battery control device according to claim 1,wherein the running state of the vehicle is a state of automatic drivingwhere a running path of the vehicle can be estimated.
 4. The vehicularbattery control device according to claim 1, wherein the running stateof the vehicle is a state before lapse of a predetermined second timefrom a timing when a shift position where the vehicle can be estimatedto be about to be parked becomes a backward position.